From a2da63758c6f7ed22eb2d595b18934cd149e0a5d Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Thu, 2 Mar 2023 14:10:53 +0000
Subject: [PATCH] Use a separate GHA cache for each matrix build (#1605)

You can't update a GHA cache once you create it, so if we use the same cache
for each job in a matrix build, then we end up populating it for the first job
that completes, so any slower jobs don't get their dependencies cached.

On the other hand, if we create 20 500MB cache items on each build, we're going
to exhaust the cache storage as soon as we do a build. So, instead, let's just
do the caching for the main branch, and hope that other branches can still
benefit from it.
---
 .github/workflows/ci.yml | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 643e3db68..6cbfa7743 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -51,6 +51,14 @@ jobs:
 
       - name: Load cache
         uses: Swatinem/rust-cache@v2
+        with:
+          # use a separate cache for each job to work around
+          # https://github.com/Swatinem/rust-cache/issues/124
+          key: "${{ matrix.name }}"
+
+          # ... but only save the cache on the main branch
+          # cf https://github.com/Swatinem/rust-cache/issues/95
+          save-if: ${{ github.ref == 'refs/head/main' }}
 
       - name: Install nextest
         uses: taiki-e/install-action@nextest
@@ -239,6 +247,14 @@ jobs:
 
       - name: Load cache
         uses: Swatinem/rust-cache@v2
+        with:
+          # use a separate cache for each job to work around
+          # https://github.com/Swatinem/rust-cache/issues/124
+          key: "${{ matrix.cmd }}"
+
+          # ... but only save the cache on the main branch
+          # cf https://github.com/Swatinem/rust-cache/issues/95
+          save-if: ${{ github.ref == 'refs/head/main' }}
 
       - name: Install nextest
         uses: taiki-e/install-action@nextest